[PATCH v9 0/2 hurd] Add irqhelp and clean up ddekit

[Damien Zammit]

Hi,

So having discussed this, we allow the irq thread to be called one more time,
but not actually call the user irq handler if the shutdown flag is set.
We acknowledge the interrupt has been handled, however.

I tested this behaviour and it works on netdde.static to ifup and ifdown,
and send a large file over ssh.

Damien